You can take my terminal when you can pry it from my cold, dead, hands.

Any one-liner you put together, you can re-run trivially. You can rerun it with modifications trivially. You can wrap it in a for loop that runs it with different parameters trivially. You can stick it in a file and make a reusable Bash script. It's far easier to show someone else how you did it (just copy/paste the text of your terminal session) than dozens of screenshots of a point-and-click adventure (and not in a good way) GUI app. Bash commands are easier over SSH than GUI apps over RDP or VNC or whatever. You can't script a GUI app.

I seriously find myself wondering why someone would use a GUI for something they can do with a terminal. Learning curve is the only reason I can think of.

I frequently find myself creating tools that let me do with a terminal what I formerly could only do with a GUI tool.